Low Feed-speed???

I understand the feed/speed rules for cutting BUT, as new person, will I have problems if I run very slow for awhile? Until I get more accustomed to all adjustments that is. For example, can I run lathe at 150rpm and just keep feed slow enough for the metal type? Or, will that somehow cause issues that I'm not aware of?

Same on mill. Can I go much slower than suggested feed/speed?

Thanks,
Regis